Multi-layer braided structures for occluding vascular defects and for occluding fluid flow through portions of the vasculature of the body

ABSTRACT

Described herein are a collapsible medical device and associated methods of occluding an abnormal opening in a body organ, wherein the medical device is shaped from plural layers of a heat-treatable metal fabric. Each of the fabric layers is formed from a plurality of metal strands and the assembly is heat-treated within a mold in order to substantially set a desired shape of the device. By incorporating plural layers in the thus-formed medical device, the ability of the device to rapidly occlude an abnormal opening in a body organ is significantly improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/618,483, filed on Sep. 14, 2012, the contents of which arehereby expressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION I. Field of the Invention

The present invention generally relates to intravascular devices fortreating certain medical conditions and, more particularly, relates to alow profile intravascular occlusion devices for treating congenitaldefects including Atrial and Ventricular Septal Defects (ASD and VSDrespectively), Patent Ductus Arteriosus (PDA) and Patent Foramen Ovale(PFD). The invention also relates to the intravascular devices used totreat arterial-venous malformations, aneurysms and other vasculardefects, or to prevent blood flow to tumors or other portions of thebody when desired. The devices made in accordance with the invention areparticularly well suited for delivery through a catheter or the like toa remote location in a patient's heart or in analogous vessels or organswithin a patient's body.

II. Description of the Related Art

A wide variety of intra cardiac prosthetic devices are used in variousmedical procedures. For example, certain intravascular devices, such ascatheters and guide wires, are generally used simply to deliver fluidsor other medical devices to specific locations within a patient's heart,such as a selective coronary artery within the vascular system. Other,frequently more complex, devices are used in treating specificconditions, such as devices used in removing vascular occlusions or fortreating septal defects and the like.

In certain circumstances, it may be necessary to occlude a patient'svessel, such as to stop blood flow through an artery to a tumor or otherlesion. Presently, this is commonly accomplished simply by inserting,for example, Ivalon particles (a trade name for vascular occlusionparticles) and short sections of coil springs into a vessel at a desiredlocation. These “embolization agents” will eventually become lodged inthe vessel, frequently floating downstream of the site at which they arereleased before blocking the vessel. This procedure is often limited inits utility, in part, due to the inability to precisely position theembolization agents. These embolization agents are not commonly used asan intra cardiac occluding device.

Physicians may temporarily occlude a septal defect until the patientstabilizes enough for open-heart surgical procedures and have usedballoon catheters similar to that disclosed by Landymore et al. in U.S.Pat. No. 4,836,204. When using such a catheter, an expandable balloon iscarried on a distal end of a catheter. When the catheter is guided tothe desired location, the balloon is inflated with a fluid until itsubstantially fills the vessel and becomes lodged therein. Resins, whichwill harden inside the balloon, such as an acrylonitrile, can beemployed to permanently fix the size and shape of the balloon. Theballoon can then be detached from the end of the catheter and left inplace. If the balloon is not filled enough, it will not be firmly lodgedin the septal defect and may rotate and loosen from the septal wall,thereby being released into the blood flowing from the right or leftventricular chamber. Overfilling the balloon is an equally undesirableoccurrence, which may lead to the rupture of the balloon and release ofresins into the patient's bloodstream.

Mechanical embolization devices, filters and traps have been proposed inthe past, representative examples of which are disclosed in King et al.,U.S. Pat. No. 3,874,388 (the '388 patent), Das, U.S. Pat. No. 5,334,217(the '217 patent), Sideris, U.S. Pat. No. 4,917,089 (the '089 patent)and Marks, U.S. Pat. No. 5,108,420 (the '420 patent). The '388, '217,'089, and '420 devices are typically pre-loaded into an introducer ordelivery catheter and are not commonly loaded by the physician duringthe medical procedure. During deployment of these devices, recaptureinto the delivery catheter is difficult if not impossible, therebylimiting the effectiveness of these devices.

Significantly, the size of these devices is inherently limited by thestructure and form of the device. When using occluding devices such asthe '089, '388, '217, or '420 plug to occlude a septal defect, thepressure and therefore the chance of dislodgment of the device increaseswith the size of the defect. Consequently, these devices must have avery large retention skirt positioned on each side of the defect.Oftentimes, the position of the septal defect dictates the size of theretention skirt. In a membranous type septal defect, it is difficult ifnot improbable to be able to effectively position the '388, '217, '089,or '420 device without at least partially closing off the aorta. Also,these disclosed devices tend to be rather expensive and time-consumingto manufacture. Hence, it is desirable to provide a low profile devicethat is recoverable and retractable into the delivery system withoutincreasing the overall thickness of the device. The desired deviceshould also be made with a relatively small retention skirt so as to bepositionable within a membranous type septal defect without closing offthe aorta.

Also, the shape of the prior art devices (for example, squares,triangles, pentagons, hexagons and octagons) requires a larger contactarea, having corners, which extend to the free wall of the atria. Eachtime the atria contracts (approximately 100,000 times per day), internalwires within the prior art devices, such as described in the Das '217patent, are flexed, creating structural fatigue fractures inapproximately 30 percent of all cases. The sharp corners of thesedevices resulted in a high percentage of cardiac perforations and theywere, therefore, withdrawn from the market. Furthermore, the previousdevices require a 14-16 French introducing catheter, making itimpossible to treat children affected with congenital defects with thesedevices.

Accordingly, it would be advantageous to provide a reliable occlusiondevice which is both easy to deploy through a 6-7 French catheter andwhich can be accurately placed in a vessel or organ. It would also bedesirable to provide a low-profile recoverable device for deployment inan organ of a patient's body.

In the Kotula et al. U.S. Pat. No. 5,846,261, there is described areliable, low-profile, intra cardiac occlusion device which may beformed to treat, for example, Ventricular Septal Defects (VSD), AtrialSeptal Defects (hereinafter ASD), and Patent Ductus Arteriosus(hereinafter PDA). When forming these intravascular devices from aresilient metal fabric a plurality of resilient strands are provided,with the wires being formed by braiding to create a resilient material.This braided fabric is then deformed to generally conform to a moldingsurface of a molding element and the braided fabric is heat treated incontact with the surface of the molding element at an elevatedtemperature. The time and temperature of the heat treatment is selectedto substantially set the braided fabric in its deformed state. After theheat treatment, the fabric is removed from contact with the moldingelement and will substantially retain its shape in the deformed state.The braided fabric so treated defines an expanded state of a medicaldevice, which can be deployed through a catheter into a channel in apatient's body.

Embodiments of the Kotula et al. invention provide specific shapes formedical devices, which may be made in accordance with that invention toaddress identified medical needs and procedures. The devices have anexpanded low-profile configuration and may include recessed clamps thatgather and hold the ends of the braided metal fabric and that attach toan end of a delivery device or guide wire, allowing recovery of thedevice after placement. In use, a guide catheter is positioned andadvanced in a patient's body such that the distal end of the catheter isadjacent a desired treatment site for treating a physiologicalcondition. A preselected medical device, made in accordance with theKotula et al. invention and having a predetermined shape, is thencollapsed by longitudinally stretching and inserted into the lumen ofthe catheter. The device is urged through the catheter and out thedistal end whereupon, due to its memory property, it will tend tosubstantially return to its expanded state adjacent the treatment site.The guide wire or delivery catheter is then released from the clamp andremoved.

In accordance with a first of these embodiments, a generally elongatemedical device has a generally tubular middle portion and a pair ofexpanded diameter portions, with one expanded diameter portionpositioned at either end of the middle portion. The width of the middleportion approximates the wall thickness of the organ to be occluded, forexample, the thickness dimension of the septum and its diameter to thesize of the defect to be occluded. The center of at least one of theexpanded diameter portions may be concentric with or offset relative tothe center of the middle portion, thereby allowing occlusion of avariety of septal defects including membranous type ventricular septaldefect, while providing a retention skirt of sufficient size to securelyclose the abnormal opening in the septum. As mentioned above, eachbraided end of the device is held together with a clamp. The clamps maybe recessed into the expanded diameter portion of the device, therebyreducing the overall length dimension of the device and creating a lowprofile occluder.

In another embodiment of the Kotula et al. invention described in the'261 patent, the medical device is generally bell-shaped, having anelongate body, a tapered first end, and a larger second end. The secondend has a fabric disc which will be oriented generally perpendicular toan axis of a channel when deployed therein. The clamps, which holdtogether the braided strand ends, are recessed toward the center of the“bell” providing a low-profile device having a reduced overall heightdimension.

The ability of the devices described in the Kotula et al. '261 patent toocclude abnormal openings in a vascular organ depend upon the pick sizeof the braided structure which, in turn, depends upon the number of wirestrands used in the braid. However, a practical limit exists on just howmany such strands can be braided. For example, if 72 bobbins are used onthe braiding machine, the resulting pick size is such that a prolongedperiod of time must elapse before total thrombosis takes place and bloodflow through the device is totally occluded. Even with 144 bobbins,blood flow is not immediately stemmed. If the pick size were effectivelyhalved by doubling the number of bobbins on the braiding machine to 288,occlusion would occur somewhat instantaneous upon placement of themedical device in the abnormal opening. However, the resulting machinesize of the braider becomes impractical from a size and cost standpoint.

As a way of reducing the time required to achieve total occlusion, theKotula et al. '261 patent teaches the concept of filling the interior ofthe medical device with an occluding fiber or an occluding fabric, suchas a polyester fabric. This occluding fiber material or fabric isgenerally hand sewn in place, which adds significantly to themanufacturing cost of the medical devices. Perhaps more importantly,adding polyester fiber or fabric in the interior of the deviceinterferes with the ability to reduce the effective diameter of thedevice upon stretching prior to loading the device into the lumen of adelivery catheter. It should be recognized that by reducing the size ofthe delivery catheter, it can be used with smaller patients.

Thus, a need exists for a way to form collapsible medical devices foroccluding abnormal openings in a vascular organ for occludingarterial-venous malformations for occluding aneurysms, for blockingblood flow to tumors or other lesions, and for otherwise blocking fluidflow through a portion of the vasculature of the body as part of amedical treatment program. Such devices ideally provide rapid occlusionfollowing delivery and placement thereof and not require the addition ofan occluding fabric placed within the interior of the medical device astaught by the prior art. The present invention provides a readilymanufacturable solution to the aforementioned problems inherent in theprior art as represented by the Kotula et al. '261 patent.

SUMMARY OF THE INVENTION

A collapsible medical device made in accordance with the presentinvention comprises multiple layers including an outer metal fabricsurrounding at least one, and possibly two or more, inner metalfabric(s) wherein each of the outer and inner metal fabrics eachcomprise a plurality of braided metal strands exhibiting an expandedpreset configuration. The collapsible medical device has proximal anddistal ends each incorporating clamps for securing the plurality ofbraided strands that comprise the inner and outer metal fabricstogether. It is to be understood that each of the several inner layersmay have their ends clamped individually and separately from the ends ofthe strands comprising the outer layer. The medical device is shaped tocreate an occlusion when in its expanded preset configuration. Theexpanded preset configuration is deformable to a lesser cross-sectionaldimension for delivery through a channel in a patient's body. Both theouter and inner metal fabrics have a memory property such that themedical device tends to return to the expanded preset configuration whenunconstrained. By braiding the inner metal fabric(s) so as to have agreater number of braided metal strands than are provided in the outermetal fabric and of a smaller wire diameter, the resulting device isstill readily deformable to a lesser cross-sectional dimension fordelivery through a channel in a patient's body, yet the increase in thetotal number of metal strands comprising the outer and inner metalfabrics result in a device that provides immediate occlusion and doesnot require a sewn-in occluding fabric. For example, the outer braidedmetal fabric may have, say, 72 strands; each of a first diameter whilethe inner metal fabric may be braided from 144 strands, each of asmaller diameter than the diameter of the strands in the outer fabriclayer. The outer metal fabric can also be braided from 144 or morestrands. One or more additional clamps may be provided intermediate thetwo ends of the device to increase the number of faces fluids which mustpass through to traverse the occlusion device. Each such face increasesthe occluding properties of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features and advantages of the invention will becomeapparent to those skilled in the art from the following detaileddescription of a preferred embodiment, especially when considered inconjunction with the accompanying drawings in which like numerals in theseveral views refer to corresponding parts.

FIG. 1 is an enlarged, side elevation view of an ASD occluderincorporating the present invention;

FIG. 2 is an enlarged front elevation view of the device of FIG. 1;

FIG. 3 is an enlarged side elevation view of the device of FIG. 1 whenlongitudinally stretched;

FIG. 4 is a right end view of the device shown in FIG. 3;

FIG. 5 is an enlarged, side elevation view of a PDA occluderincorporating the present invention;

FIG. 6 is a right end view of the device of FIG. 5; and

FIG. 7 is a greatly enlarged view like that of FIG. 6.

FIG. 8 shows a multi-layered vascular plug.

FIG. 9 shows the plug of FIG. 8 in combination with a center clamp.

FIG. 10 shows an alternative multi-layered vascular plug.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a percutaneous catheter directedocclusion device for use for creating an occlusion in the vasculature ofa patient's body. Thus, embodiments of the present invention may be usedin occluding an abnormal opening in a patients' body, such as an AtrialSeptal Defect (ASD), a ventricular septal defect (VSD), a Patent Ductusarteriosus (PDA), a Patent Foramen Ovale (PFO), and the like. They mayalso be used to block flow through a vein, artery or other vessel. Assuch, such embodiments may also be used in fabricating a flow restrictoror an aneurysm bridge or other types of vascular plugs and occluders forplacement in the vascular system. In forming a medical device, via themethod of the invention, a planar or tubular metal fabric is provided.The planar and tubular fabrics are formed of a plurality of wire strandshaving a predetermined relative orientation between the strands. Thetubular fabric has metal strands which define two sets of essentiallyparallel generally helical strands, with the strands of one set having a“hand”, i.e. a direction of rotation, opposite that of the other set.This tubular fabric is known in the fabric industry as a tubular braid.

The pitch of the wire strands (i.e. the angle defined between the turnsof the wire and the axis of the braid) and the pick of the fabric (i.e.the number of turns per unit length) as well as some other factors, suchas the number of wires employed in a tubular braid and their diameter,are important in determining a number of properties of the device. Forexample, the greater the pick and pitch of the fabric, and hence thegreater the density of the wire strands in the fabric, the stiffer thedevice will be. Having a greater wire density will also provide thedevice with a greater wire surface area, which will generally enhancethe tendency of the device to occlude a blood vessel in which it isdeployed. This thrombogenicity can be either enhanced by, e.g. a coatingof a thrombolytic agent, or abated, e.g. by a coating of a lubricious,antithrombogenic compound. When using a tubular braid to form a deviceof the Kotula '261 patent, a tubular braid of about 4 mm in diameterwith a pitch of about 50° and a pick of about 74 (per linear inch) wouldseem suitable for fabricating devices capable of occluding abnormalopenings of about 2 mm to about 4 mm in inner diameter. However, theocclusion may not be immediate.

A metal planar fabric is a more conventional fabric and may take theform of a flat woven sheet, knitted sheet or the like. In the wovenfabric there are typically two sets of generally metal strands, with oneset of strands being oriented at an angle, e.g. generally perpendicular(having a pick of about 90°), with respect to the other set. As notedabove, the pitch and pick of the fabric (or, in the case of a knitfabric, the pick and the pattern of the knit, e.g. Jersey or doubleknits) may be selected to optimize the desired properties of theresulting medical device.

The wire strands of the planar or tubular metal fabric are preferablymanufactured from so-called shape memory alloys. Such alloys tend tohave a temperature induced phase change which will cause the material tohave a preferred configuration which can be fixed by heating thematerial above a certain transition temperature to induce a change inthe phase of the material. When the alloy is cooled back down, the alloywill “remember” the shape it was in during the heat treatment and willtend to assume that configuration unless constrained from so doing.

Without any limitation intended, suitable wire strand materials may beselected from a group consisting of a cobalt-based low thermal expansionalloy referred to in the field as ELGELOY, nickel-based high temperaturehigh-strength “superalloys” commercially available from HaynesInternational under the trade name HASTELLOY, nickel-based heattreatable alloys sold under the name INCOLOY by International Nickel,and a number of different grades of stainless steel. The importantfactor in choosing a suitable material for the wire strands is that thewires retain a suitable amount of the deformation induced by a moldingsurface (as described below) when subjected to a predetermined heattreatment.

In the preferred embodiment, the wire strands are made from a shapememory alloy, NiTi (known as Nitinol) that is an approximatelystoichiometric alloy of nickel and titanium and may also include otherminor amounts of other metals to achieve desired properties. Handlingrequirements and variations of NiTi alloy composition are known in theart, and therefore such alloys need not be discussed in detail here.U.S. Pat. No. 5,067,489 (Lind) and U.S. Pat. No. 4,991,602 (Amplatz etal.), the teachings of which are incorporated herein by reference,discuss the use of shape memory NiTi alloys in guide wires. Such NiTialloys are preferred, at least in part, because they are commerciallyavailable and more is known about handling such alloys than other knownshape memory alloys. NiTi alloys are also very elastic and are said tobe “super elastic” or “pseudoelastic”. This elasticity allows a deviceof the invention to return to a preset expanded configuration fordeployment.

When forming a medical device in accordance with the present invention,rather than having a single braided fabric layer, a plurality ofappropriately sized pieces of tubular or planar metal fabric areappropriately layered with respect to one another and inserted into thesame mold, whereby the fabric layers deform to generally conform to theshape of the cavities within the mold. The shape of the cavities is suchthat the plural metal fabric layers deform into substantially the shapeof the desired medical device. The ends of the wire strands of thetubular or planar metal fabric layers should be secured to prevent themetal fabrics from unraveling. A clamp or welding, as further describedbelow, may be used to secure the ends of the wire strands. Theadvantages of the present invention can also be achieved byheat-treating the inner and outer fabric layers separately and theninserting the inner layer or layers within the confines of the outerlayer. It is further contemplated that the inner and outer fabric layersmay be heat-set into different geometries and then assembled one withinthe other.

In the case of a tubular braid, a molding element may be positionedwithin the lumen of the braid prior to insertion into the mold tothereby further define the molding surface. If the ends of the tubularmetal fabric have already been fixed by a clamp or welding, the moldingelement may be inserted into the lumen by manually moving the wirestrands of the fabric layers apart and inserting the molding elementinto the lumen of the innermost tubular fabric. By using such a moldingelement, the dimensions and shape of the finished medical device can befairly accurately controlled and ensures that the fabric conforms to themold cavity.

The molding element may be formed of a material selected to allow themolding element to be destroyed or removed from the interior of themetal fabric. For example, the molding element may be formed of abrittle, frangible or friable material. Once the material has beenheat-treated in contact with the mold cavities and molding element, themolding element can be broken into smaller pieces, which can be readilyremoved from within the metal fabric. If this material is glass, forexample, the molding element and the metal fabric can be struck againsta hard surface, causing the glass to shatter. The glass shards can thenbe removed from the enclosure of the metal fabric.

Alternatively, the molding element can be formed of a material that canbe chemically dissolved, or otherwise broken down, by a chemical agentthat will not substantially adversely affect the properties of the metalwire strands. For example, the molding element can be formed of atemperature resistant plastic resin that is capable of being dissolvedwith a suitable organic solvent. In this instance, the fabric and themolding element can be subjected to a heat treatment to substantiallyset the shape of the fabric in conformance with the mold cavity andmolding element, whereupon the molding element and the metal fabric canbe immersed in the solvent. Once the molding element is substantiallydissolved, the metal fabric can be removed from the solvent.

Care should be taken to ensure that the materials selected to form themolding element are capable of withstanding the heat treatment withoutlosing their shape, at least until the shape of the multiple fabriclayers has been set. For example, the molding element could be formed ofa material having a melting point above the temperature necessary to setthe shape of the wire strands, but below the melting point of thestrands forming the metal fabric layers. The molding element and thelayers of metal fabric ultimately comprising the medical device can thenbe heat treated to set the shape of the metal fabric, whereupon thetemperature can be increased to substantially completely melt themolding element, thereby removing the molding element from within themetal fabric. Those skilled in the art will appreciate that the shapesof the mold cavities and the molding elements may be varied in order toproduce the medical device having a preselected size and shape.

It should be understood that the specific shape of a particular moldingelement produces a specific shape and other molding elements havingdifferent shape configurations may be used as desired. If a more complexshape is desired, the molding element and mold may have additional partsincluding a camniing arrangement, but if a simpler shape is beingformed, the mold may have few parts. The number of parts in a given moldand the shapes of those parts will be dictated almost entirely by theshape of the desired medical device to which the metal fabric willgenerally conform.

When the multiple layers of tubular braid, for example, are in theirrelaxed configuration, the wire strands forming the tubular braids willhave a first predetermined relative orientation with respect to oneanother. As the tubular braids are compressed along their axis, thefabric layers will tend to flare out away from the axis conforming tothe shape of the mold. When so deformed, the relative orientation of thewire strands of the metal fabric layers will change. When the mold isassembled, the outer and inner metal fabrics will generally conform tothe molding surface of the cavity. The medical device has a presetexpanded configuration and a collapsed configuration which allows thedevice to be passed through a catheter or other similar delivery device.The shape of the fabric layers generally defines the expandedconfiguration when they are deformed to generally to conform to themolding surface of the mold.

Once the tubular or planar metal fabric layers are properly positionedwithin a preselected mold with the metal fabric layers generallyconforming to the molding surface of the cavities therein, the fabriclayers can be subjected to a heat treatment while they remain in contactwith the molding surface. Heat-treating the metal fabric comprising theplural layers substantially sets the shapes of the wire strands fromwhich they are braided in a reoriented relative position when the fabriclayers conform to the molding surface. When the medical device isremoved from the mold, the fabric layers retain the shape of the moldingsurfaces of the mold cavities to thereby define a medical device havinga desired shape. This heat treatment will depend in large part upon thematerial of which the wire strands of the metal fabric layers areformed, but the time and temperature of the heat treatment should beselected to substantially set the fabric layers in their deformed state,i.e., wherein the wire strands are in their reoriented relativeconfiguration and the fabric layers generally conform to the moldingsurface.

After the heat treatment, the device is removed from contact with themold surfaces and will substantially retain its shape in a deformedstate. If a molding element is used, this molding element can be removedas described above.

The time and temperature of the heat treatment can very greatlydepending upon the material used in forming the wire strands. As notedabove, one preferred class of materials for forming the wire strands areshape memory alloys, with Nitinol, a nickel titanium alloy, beingparticularly preferred. If Nitinol is used in making the wire strands ofthe fabric layers, the wire strands will tend to be very elastic whenthe metal is in its austenitic phase; this very elastic phase isfrequently referred to as a super elastic or pseudo elastic phase. Byheating the Nitinol above a certain phase transition temperature, thecrystal structure of the Nitinol metal will tend to “set” the shape ofthe fabric layers and the relative configuration of the wire strands inthe positions in which they are held during the heat treatment.

Suitable heat treatments of Nitinol wire to set a desired shape are wellknown in the art. Spirally wound Nitinol coils, for example, are used ina number of medical devices, such as in forming the coils commonlycarried around distal links of guide wires and in forming other medicalproducts known in the art. A wide body of knowledge exists for formingNitinol in such devices, so there is no need to go into great detailhere on the parameters of a heat treatment for the Nitinol fabricpreferred for use in the present invention.

Briefly, though, it has been found that holding a Nitinol fabric atabout 500 degrees centigrade to about 550 degrees centigrade for aperiod of about 1 to 30 minutes, depending upon the size of the mold andthe stiffness of the device to be made will tend to set the fabriclayers in their deformed state, i.e., wherein they conform to themolding surface of the mold cavities. At lower temperatures, the heattreatment time will tend to be greater and at higher temperatures thetime will tend to be shorter. These parameters can be varied asnecessary to accommodate variations in the exact composition of theNitinol, prior heat treatment of the Nitinol, the desired properties ofthe Nitinol in the finished article, and other factors which will bewell known to those skilled in this field.

Instead of relying on convection heating or the like, it is also knownin the art to apply an electrical current to the Nitinol to heat it. Inthe present invention, this can be accomplished by, for example,connecting electrodes to opposed ends of the metal fabric layers.Resistance heating in order to achieve the desired heat treatment, whichwill tend to eliminate the need to heat the entire mold to the desiredheat-treating temperature, can then heat the wire. The materials,molding elements and methods of molding a medical device from a tubularor planar metal fabric is further described in U.S. Pat. Nos. 5,725,552,5,944,738 and 5,846,261 and assigned to the same assignee as the presentinvention, the entire disclosures of which are incorporated herein byreference.

Once a device having a preselected shape has been formed, the device maybe used to treat a physiological condition of a patient. A medicaldevice suitable for treating the condition, which may be substantiallyin accordance with one of the embodiments outlined below, is selected.Once the appropriate medical device is selected, a catheter or othersuitable delivery device may be positioned within a channel in apatient's body to place the distal end of the delivery device adjacentthe desired treatment site, such as immediately adjacent (or evenwithin) the shunt of an abnormal opening in the patient's organ forexample.

The delivery device (not shown) can take any suitable shape, butdesirably comprises an elongate flexible metal shaft having a threadeddistal end for engagement with a threaded bore formed in the clamp ofthe medical device. The delivery device can be used to urge the medicaldevice through the lumen of a catheter for deployment in ‘a channel of apatient's body. When the medical device is deployed out the distal endof the catheter, the delivery device still will retain it. Once themedical device is properly positioned within the shunt of the abnormalopening, the shaft of the delivery device can be rotated about its axisto unscrew the medical device from the delivery means.

By keeping the medical device attached to the delivery means, theoperator can retract the device for repositioning relative to theabnormal opening, if it is determined that the device is not properlypositioned within the shunt. A threaded clamp attached to the medicaldevice allows the operator to control the manner in which the medicaldevice is deployed out the distal end of the catheter. When the medicaldevice exits the catheter, it will tend to resiliently return to apreferred expanded shape, which is set when the fabric is heat-treated.When the device springs back into this shape, it may tend to act againstthe distal end of the catheter effectively urging itself forward beyondthe end of the catheter. This spring action could conceivably result inimproper positioning of the device if the location of the device withina channel is critical, such as where it is being positioned in a shuntbetween two vessels. Since the threaded clamp can enable the operator tomaintain a hold on the device during deployment, the spring action ofthe device can be controlled by the operator to ensure properpositioning during deployment.

The medical device can be collapsed into its reduced diameterconfiguration and inserted into the lumen of the catheter. The collapsedconfiguration of the device may be of any shape suitable for easypassage through the lumen of a catheter and proper deployment out thedistal end of the catheter. For example, an ASD occluding device mayhave a relatively elongated collapsed configuration wherein the devicesare stretched along their axes. This collapsed configuration can beachieved simply by stretching the device generally along its axis, e.g.by manually grasping the clamps and pulling them apart, which will tendto collapse the expanded diameter portions of the device inwardly towardthe device's axis. A PDA occlusion device also operates in much the samefashion and can be collapsed into its collapsed configuration forinsertion into the catheter by applying tension generally along the axisof the device. In this regard, these devices are not unlike “Chinesehandcuffs”, which tend to constrict in diameter under axial tension.

If the device is to be used to permanently occlude a channel in thepatient's body, one can simply retract the catheter and remove it fromthe patient's body. This will leave the medical device deployed in thepatient's vascular system so that it may occlude the blood vessel orother channel in the patient's body. In some circumstances, the medicaldevice may be attached to a delivery system in such a manner as tosecure the device to the end of the delivery means. Before removing thecatheter in such a system, it may be necessary to detach the medicaldevice from the delivery means before removing the catheter and thedelivery means.

Although the device will tend to resiliently return to its initialexpanded configuration, i.e., its shape prior to being collapsed forpassage through the catheter, it should be understood that it might notalways return entirely to that shape. For example, it may be desirablethat the device has a maximum outer diameter in its expandedconfiguration at least as large as and preferably larger than, the innerdiameter of the lumen of the abnormal opening in which it is to bedeployed. If such a device is deployed in a vessel or abnormal openinghaving a small lumen, engagement with the lumen will prevent the devicefrom completely returning to its expanded configuration. Nonetheless,the device would be properly deployed because it would engage the innerwall of the lumen to seat the device therein.

When the device is deployed in a patient, thrombi will tend to collecton the surface of the wires. By having a greater wire density asafforded by the multiple layer construction of the present invention,the total surface area of the wires will be increased, increasing thethrombotic activity of the device and permitting it to relativelyrapidly occlude the vessel in which it is deployed. It is believed thatforming the occlusion device with the outermost layer being 4 mmdiameter tubular braid whose strands are about 0.004 inch in diameterand having a pick of at least about 40 and a pitch of at least about 30°and surrounding an inner tubular braid whose strands are about 0.001inch and of the same pick and pitch will provide sufficient surface areato substantially completely occlude an abnormal opening or blood vesselof 2 mm to about 4 mm in inner diameter in a very short period of time.If it is desired to increase the rate at which the device occludes, athird or forth concentrically disposed braided layer can be added.

Referring now to the drawings, a discussion of the embodiments of themedical device of the present invention will next be presented. FIGS.1-4 illustrate a first preferred embodiment of a medical device 10constructed in accordance with the present invention for correcting anatrial septal defect (ASD). With reference to FIGS. 1-4, the device 10is shown greatly enlarged so that the multiple layers comprising themedical device can be viewed. The ASD device is in its relaxed,non-stretched state with two aligned disks 12 and 14 linked together bya short middle cylindrical section 16 (FIG. 3). It is proposed that thisdevice 10 may also be well suited in occluding defects known in the artas patent foramen ovale (hereinafter PFO). Those skilled in the art willappreciate that a device of this configuration may also be suitable foruse in a transcatheter closure during a Fenestrated Fontan's procedure.ASD is a congenital abnormality of the atrial septum characterized bystructural deficiency of the atrial septum. A shunt may be present inthe atrial septum, allowing flow between the right and left atrialchambers of the heart. In large defects with significant left to rightshunts through the defect, the right atrium and right ventricle arevolume overloaded and the augmented volume is ejected into alow-resistance pulmonary vascular bed.

Pulmonary vascular occlusive disease and pulmonary atrial hypertensiondevelops in adulthood. Patients with secundum ASD with a significantshunt (defined as a pulmonary blood flow to systemic blood flow ratio ofgreater than 1.5) are operated upon ideally at two to five years of ageor whenever a diagnosis is made in later years. With the advent of twodimensional echocardiography and Doppler color flow mapping, the exactanatomy of the defect can be visualized. The size of the defect asdetermined by balloon measurement will correspond to the selected sizeof the ASD device 10 to be used.

The device 10, shown in its unconfined or relaxed state in FIGS. 1 and2, is adapted to be deployed within the shunt comprising an ASD or aPFO. For exemplary purposes, use of the device 10 in an ASD closureprocedure is described in the Kotula '261 patent referenced above andthose wishing further information are referred to that patent. Turningfirst to the constructional features of the device 10, the ASD occluderis sized in proportion to the shunt to be occluded. In the relaxedorientation, the metal fabric is shaped such that two disk like members12 and 14 are axially aligned and linked together by the shortcylindrical segment 16. The length of the cylindrical segment 16 whennot stretched preferably approximates the thickness of the atrialseptum, and ranges between 3 to 5 mm. The proximal disk 12 and distaldisk 14 preferably have an outer diameter sufficiently larger than theshunt to prevent dislodging of the device. The proximal disk 14 has arelatively flat configuration, whereas the distal disk 12 is preferablycupped towards the proximal end slightly overlapping the proximal disk14. In this manner, the spring action of the device 10 will cause theperimeter edge 18 of the distal disk to fully engage the sidewall of theseptum and likewise an outer edge of the proximal disk 14 will fullyengage an opposite sidewall of the septum.

In accordance with the present invention, the device 10 comprises anouter braided layer 20, a first inner layer 22 and possibly an optionalthird and innermost layer 24, thereby significantly increasing the wiredensity without unduly increasing the stiffness of the device or itsability to assume a decreased outer diameter upon longitudinalstretching. Multiple inner layers may be used as needed.

The ends of the tubular braided metal fabric device 10 are welded orclamped together with clamps as at 26, to avoid fraying. The ends of allof the layers may be grouped together and secured by two clamps, one ateach end or separate clamps can be applied on each end of the individuallayers. Of course the ends may alternately be held together by othermeans readily known to those skilled in the art. The clamp 26 tyingtogether the wire strands of the multiple layers at one end also servesto connect the device to a delivery system. In the embodiment shown inFIG. 1, the clamp 26 is generally cylindrical in shape and has a recess(not shown) for receiving the ends of the metal fabric to substantiallyprevent the wires comprising the woven fabric from moving relative toone another. The clamp 26 also has a threaded bore 28. The threaded boreis adapted to receive and engage a threaded distal end of a deliverydevice, such as a pusher wire.

The ASD occlusion device 10 of this embodiment of the invention canadvantageously be made in accordance with the method outlined above. Theouter layer 20 of device 10 is preferably made from a 0.004-0.008 inchdiameter Nitinol wire strands, but lesser or greater diameter strandscan be used as well. The braiding of the wire mesh comprising the outerlayer may be carried out with 28 picks per inch at a shield angle ofabout 64 degrees using a Maypole braider with 72 wire carriers. Thebraided layers 22 and 24 may each comprise 144 strands of Nitinol wireof a diameter in a range of from 0.001 inch to 0.002 inch, braided atthe same pitch. The stiffness of the ASD device 100 may be increased ordecreased by altering the wire size, the shield angle, the pick rate,and the number of wire carriers or the heat treatment process. Thoseskilled in the art will recognize from the preceding discussion that thecavities of a mold must be shaped consistent with the desired shape ofthe ASD device. Also, it will be recognized that certain desiredconfigurations may require that portions of the cavities be cammed. FIG.3 illustrates the ASD device 10 in a somewhat longitudinally stretchedstate. The distance separating the distal and proximal disks 12 and 14is preferably equal or slightly less than the length of the cylindricalsegment 16. The cup shape of each disk 12 and 14, ensures completecontact between the outer edge of each disk 12 and 14 and the atrialseptum. Upon proper placement, a new endocardial layer of endothelialcells forms over the occlusion device 10, thereby reducing the chance ofbacterial endocarditic and thromboembolisms.

The distance separating the disks 12 and 14 of occluding device 10 maybe increased to thereby provide an occluding device suitable for use inoccluding a channel within a patient's body, having particularadvantages in use as a vascular occlusion device. The device 10 includesa generally tubular middle portion 16 and a pair of expanded diameterportions 12 and 14. The expanded diameter portions are disposed ateither end of the generally tubular middle portion. The relative sizesof the tubular middle section 16 and the expanded diameter portions12-14 can be varied as desired. The medical device can be used as avascular occlusion device to substantially stop the flow of bloodthrough a patient's blood vessel. When the device 10 is deployed withina patient's blood vessel, it is positioned within the vessel such thatits longitudinal axis generally coincides with the axis of the vesselsegment in which it is being inserted. The dumbbell shape is intended tolimit the ability of the vascular occlusion device to turn at an anglewith respect to the axis of the blood vessel to ensure that it remainsin substantially the same position in which the operator deploys itwithin the vessel.

In order to relatively strongly engage the lumen of the blood vessel,the maximum diameter of the expanded diameter portions 12-14 should beselected so that it is at least as great as the diameter of the lumen ofthe vessel in which it is to be deployed and is optimally slightlygreater than that diameter. When it is deployed within the patient'svessel, the vascular occlusion device will engage the lumen at twospaced apart locations. The device is desirably longer along its axisthan the dimensions of its greatest diameter. This will substantiallyprevent the vascular occlusion device 10 from turning within the lumenat an angle to its axis, essentially preventing the device from becomingdislodged and tumbling along the vessel within the blood flowing throughthe vessel.

The relative sizes of the generally tubular middle portion 16 andexpanded diameter portions 12-14 of the vascular occlusion device can bevaried as desired for any particular application by appropriateselection of a mold to be used during the heat setting of the device.For example, the outer diameter of the middle portion 16 may rangebetween about ¼ and about ⅓ of the maximum diameter of the expandeddiameter portions and the length of the middle portion 16 may compriseabout 20% to about 50% of the overall length of the device 10. Althoughthese dimensions are suitable if the device is to be used solely foroccluding a vascular vessel, it is to be understood that thesedimensions may be varied if the device is to be used in otherapplications, such as a ventricular septal defect occluder (VSD).

The aspect ratio (i.e., the ratio of the length of the device over itsmaximum diameter or width) of the device 10 illustrated in thisembodiment is desirably at least about 1.0, with a range of about 1.0 toabout 3.0 being preferred and then aspect ratio of about 2.0 beingparticularly preferred. Having a greater aspect ratio will tend toprevent the device 10 from rotating generally perpendicularly to itsaxis, which may be referred to as an end-over-end roll. So long as theouter diameter of the expanded diameter portions 12-14 of the device 10is large enough to seat the device fairly securely against the lumen ofthe channel in which the device is deployed, the inability of the deviceto turn end-over-end will help keep the device deployed precisely whereit is positioned within the patient's vascular system or in any otherchannel in the patient's body. Alternatively, having expanded diameterportions 12-14 which have natural relaxed diameters substantially largerthan a lumen of the vessels in which the device is deployed should alsosuffice to wedge the device into place in the vessel without undueconcern being placed on the aspect ratio of the device.

Referring next to FIGS. 5-9, there is shown generally a device 100suitable for occluding a patent ductus arteriosus (PDA). PDA isessentially a condition wherein two blood vessels, the aorta and thepulmonary artery adjacent the heart, have a shunt between theirrespective lumens. Blood can flow directly between these two bloodvessels through the shunt, resulting in cardiac failure and pulmonaryvascular disease. The PDA device 100 has a generally bell-shaped body102 and an outwardly flaring forward end 104. The bell-shaped body 102is adapted to be positioned within the aorta to help seat the body ofthe device in the shunt. The sizes of the body 102 and the end portion104 can be varied as desired during manufacture to accommodate differentsized shunts. For example, the body 102 may have a diameter along itsgenerally slender middle of about 10 mm and a length along its axis ofabout 25 mm. In such a medical device 100, the base of the body mayflare generally radially outward until it reaches an outer diameterequal to that of the forward end 104 which may be on the order of about20 mm in diameter.

The base 106 desirably flares out relatively rapidly to define ashoulder 108, tapering radially outwardly from the body 102. When thedevice 100 is deployed in a vessel, this shoulder 108 will abut theperimeter of the lumen being treated with higher pressure. The forwardend 104 is retained within the vessel and urges the base of the body 102open to ensure that the shoulder 108 engages the wall of the vessel toprevent the device from becoming dislodged from within the shunt.

A PDA occlusion device 100 of this embodiment of the invention canadvantageously be made in accordance with the method outlined above,namely deforming multiple layers 110, 112 and 114 (FIG. 7) of generallyconcentrically oriented tubular metal fabric to conform to a moldingsurface of a mold and heat-treating the fabric layers to substantiallyset the fabric layers in their deformed state. With continued referenceto the greatly enlarged view of FIG. 7, the outer layer 110 comprises aframe that defines the outer shape of the medical device 100. It ispreferably formed from 72 or 144 braided strands whose diameters are ina range of from 0.003 to about 0.008 inch. The pitch of the braid may bevariable. Within this frame is the layer 112 that forms an outer liner.It may also prove expedient to incorporate a third layer 114 as an innerliner. The outer and inner liners may be braided using 144 strands of ashape memory wire whose diameter may be 0.001 to 0.002 inch. The pitchof the braid in layers 112 and 114 should be the same. As noted above,the ends 116 and 118 of the braided layers should be secured in order toprevent the braids from unraveling. In the preferred embodiment, clamps120 are used to tie together the respective ends of the wire strands oneach end 116 and 118 of the tubular braid members forming the occlusiondevice 100. Alternatively, different clamps may be used to secure theends of the metal strands of the outer fabric layer than are used tosecure the ends of the metal strands of each of the inner layers. It isto be understood that other suitable fastening means may be attached tothe ends in other ways, such as by welding, soldering, brazing, use ofbiocompatable cementious material or in any other suitable fashion. Oneor both clamps 120 of the outer layer may include a threaded bore 122that serves to connect the device 100 to a delivery system (not shown).In the embodiment shown, the clamps 120 are generally cylindrical inshape and have a crimping recess for receiving the ends of the wirestrands to substantially prevent the wires from moving relative to oneanother.

When using untreated NiTi fabrics, the strands will tend to return totheir unbraided configuration and the braided layers 110, 112 and 114can unravel fairly quickly unless the ends of the length of the braidedlayers that are cut to form the device are constrained relative to oneanother. The clamps 120 are useful to prevent the layers of braid fromunraveling at either end. Although soldering and brazing of NiTi alloyshas proven to be fairly difficult, the ends can be welded together, suchas by spot welding with a laser welder. When cutting the fabriccomprising the multiple layers 110, 112 and 114 to the desireddimensions, care should be taken to ensure that the fabric layers do notunravel. In the case of tubular braids formed of NiTi alloys, forexample, the individual strands will tend to return to their heat setconfiguration unless constrained. If the braid is heat treated to setthe strands in the braided configuration, they will tend to remain inthe braided form and only the ends will become frayed. However, it maybe more economical to simply form the braid without heat-treating thebraid since the fabric will be heat treated again in forming the medicaldevice.

Once the fabric is compressed so as to conform to the walls defining themold interior, the fabric layers can be subjected to a heat treatmentsuch as is outlined above. When the mold is open again the fabric willgenerally retain its deformed, compressed configuration. The formeddevice 100 can be collapsed, such as by urging the clamps 120 generallyaxially away from one another, which will tend to collapse the device100 toward its axis. The collapsed device can then be attached to adelivery device, such as an elongated flexible push wire and passedthrough a delivery catheter for deployment in a preselected site in thepatient's body. The use of the resulting device to occlude a PDA is thesame as has been described in the Kotula '261 patent and need not berepeated here.

Because of the significant increase in the number of wire strands in thecomposite multi-layer structure, it is no longer necessary toincorporate a sewn-in polyester material in order to reduce the timerequired to establish total occlusion of a PDA. This not only reducesthe cost of manufacture but also facilitates loading of the resultingdevice into a delivery catheter of a reduced French size. Reduced Frenchsize means ability to treat smaller patents which is a major advantage.

FIGS. 8-10 show various vascular plug arrangements. These plugs areideally suited for treating a variety of arterial-venous malformationsand aneurysms. These plugs can also be used to block blood flow to atumor or lesion. Likewise, these plugs can be used to bloc fluid flowthrough a portion of the vasculature of the body in connection with thetreatment of other medical conditions.

Each embodiment shown in FIGS. 8-10 has a multi-layered braidedstructure 150, i.e., two or more layers of braided fabric. When themulti-layered braided structure has a tubular shape, a pair of endclamps 152 and 154 are provided to prevent the multi-layered braidedstructure from unraveling. Those skilled in the art will recognize thatonly a single end clamp is required if the braids are in the form of asack as opposed to having a tubular shape.

The embodiment shown in FIG. 8 has a cylindrical wall 155 with two faces156 and 158 at the opposite ends. Generally speaking, when the device isin its expanded configuration as shown in FIG. 8, the cylindrical wallabuts the wall of the vessel in which the device is deployed to hold thedevice in place. The two faces 156 and 158 preclude fluid flow past thedevice.

In some treatment situations, it may be desirable to increase the numberof faces to increase the ability of the device to block fluid flow pastthe device. FIGS. 9 and 10 show how this can be accomplished.

The device shown in FIG. 9 also has a cylindrical wall 155, a proximalface 156 and a distal face 158. The embodiment of FIG. 9 furtherprovides an intermediate clamp 160 clamping an intermediate portion ofthe multi-braided material. This divides the cylindrical wall into twosections 155 a and 155 b and forming two additional faces 162 and 164.When the device of FIG. 9 is deployed, the two sections 155 a and 155 bof cylindrical wall 155 still abuts the vessel wall to hold the devicein place yet fluid must to traverse all for faces (namely faces 156,158, 162 and 164) to flow past the device. The reduction in flowprovided by the two additional faces 162 and 164 can result in fasterclotting.

FIG. 10 shows the same basic structure as FIG. 9. The primary differenceis that the application of the intermediate clamp 160 results in the twosections 155 a and 155 b having a bulbous rather than a cylindricalform. The widest part of sections 155 a and 155 b still engage thevessel wall and hold the device in place after deployment. There arealso still four faces (156, 158, 162 and 164) even though they arecurved as opposed to flat as shown in FIG. 9.

The intermediate clamp 160 can be made of any suitable material. Suturethread has proven to be effective. The two end clamps 152 and 154 arepreferably made of a radiopaque material so they can easily bevisualized using, for example, a fluoroscope. The intermediate clamp canbe made of such material as well. Also, additional intermediate clampscan be added to further increase the number of faces. For example, iftwo intermediate clamps are used, a total of six faces would be present.With each additional clamp, two additional faces are provided.

Also, when the multi-layered braided structure (or at least one of thelayers thereof) is made of a superelastic or shape memory material, itmay be possible to eliminate the intermediate clamps and instead moldthe device to have such a shape (e.g., a shape such as that shown inFIG. 8) when fully deployed and in its expanded preset configuration. Ofcourse, all such embodiments, including those shown in FIGS. 8-10, aredeformable to a lesser cross-sectional dimension for delivery through acatheter.

This invention has been described herein in considerable detail in orderto comply with the Patent Statutes and to provide those skilled in theart with the information needed to apply the novel principles and toconstruct and use embodiments of the example as required. However, it isto be understood that specifically different devices can carry out theinvention and that various modifications can be accomplished withoutdeparting from the scope of the invention itself.

What is claimed is:
 1. A medical device comprising: an outer fabriclayer surrounding at least one inner fabric layer, each of the outerfabric layer and the at least one inner fabric layer comprising aplurality of braided strands extending from a proximal end to a distalend of each of the outer fabric layer and the at least one inner fabriclayer, the outer fabric layer and the at least one inner fabric layerhaving an expanded preset configuration, the expanded presetconfiguration comprising at least one expanded diameter portionconfigured to be constrained to a lesser cross-sectional dimension fordelivery to a treatment site in a patient's body, the outer fabric layerand the at least one inner fabric layer having a memory property suchthat the at least one expanded diameter portion tends to return to theexpanded preset configuration when unconstrained.
 2. The medical deviceas in claim 1, wherein the at least one expanded diameter portion isdisk shaped.
 3. The medical device as in claim 1, wherein the at leastone expanded diameter portion is cylindrical shaped.
 4. The medicaldevice as in claim 1, wherein the at least one expanded diameter portionis bell shaped.
 5. The medical device as in claim 1, further comprisinga plurality of expanded diameter portions.
 6. The medical device as inclaim 5, wherein the plurality of expanded diameter portions have thesame outer diameter.
 7. The medical device as in claim 5, wherein theplurality of expanded diameter portions have different outer diameters.8. The medical device as in claim 5, wherein the plurality of expandeddiameter portions have similar shapes.
 9. The medical device as in claim5, wherein a pair of the plurality of expanded diameter portions arejoined by a segment having a smaller outer diameter than each of thepair of expanded diameter portions.
 10. The medical device as in claim9, wherein the medical device comprises a proximal face, a distal face,and at least two intermediate faces disposed between the proximal faceand the distal face.
 11. The medical device as in claim 1, whereinproximal ends of the plurality of braided strands of the outer fabriclayer and the at least one inner fabric layer are secured together. 12.The medical device as in claim 1, wherein distal ends of the pluralityof braided strands of the outer fabric layer and the at least one innerfabric layer are secured together.
 13. The medical device as in claim 1,wherein proximal ends and the distal ends of the plurality of braidedstrands of the outer fabric layer and the at least one inner fabriclayer are secured together.
 14. The medical device as in claim 1,wherein a pitch of the plurality of braided strands comprising the outerfabric layer and the at least one inner fabric layer are generallyequal.
 15. The medical device as in claim 1, wherein the braided strandscomprising the outer fabric layer are of a larger diameter than thebraided strands comprising the at least one inner fabric layer.
 16. Themedical device as in claim 1, wherein a number of braided strandscomprising the at least one inner fabric layer is greater than a numberof braided strands comprising the outer fabric layer.
 17. The medicaldevice as in claim 1, further comprising a third fabric layer disposedwithin the at least one inner fabric layer, the third fabric layercomprising a plurality of braided strands.
 18. The medical device as inclaim 17, wherein the plurality of braided strands of the third fabriclayer comprise proximal ends and distal ends.
 19. The medical device asin claim 18, wherein at least one of the proximal ends and the distalends of the plurality of braided strands of each of the outer fabriclayer, the at least one inner fabric layer, and the third fabric layerare secured together.
 20. The medical device as in claim 18, wherein thethird fabric layer has an expanded preset configuration corresponding tothe expanded preset configuration of the outer fabric layer and the atleast one inner fabric layer.